Heat-resistant brittle label

ABSTRACT

A laser-markable, acrylic resin-based laminate having a thickness of 100 to 200 μm and including (A3) a pigmented layer made of a crosslinked acrylic resin obtained by crosslinking an acrylic resin composition having a hydroxyl value of 10 to 100 mg KOH/g, (B3) a base layer made of a crosslinked acrylic resin obtained by crosslinking an acrylic resin composition having a hydroxyl value of 18 to 40 mg KOH/g, and (C3) a destructible layer made of a crosslinked acrylic resin obtained by crosslinking a mixture of an acrylic resin composition having a hydroxyl value of 20 to 35 mg KOH/g and polymer beads.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of co-pending application Ser. No.12/670,288 filed on Jan. 22, 2010, which is a National Stage ofPCT/JP2008/057130 filed on Apr. 11, 2008 which claims foreign priorityto Japanese Application No's 2007-191330, 2006-283051 and 2006-283052filed on Jul. 23, 2007, Oct. 17, 2006 and Oct. 17, 2006, respectively.The entire content of each of these applications is hereby expresslyincorporated by reference.

TECHNICAL FIELD

This invention relates to a laser-markable laminate that can be markedwith laser light. More particularly, it relates to a laser-markablelaminate that is convenient to be attached to a substrate and, afterattachment to a substrate, withstands long use under a high temperaturecondition, particularly at or above 150° C. and becomes non-reusable onbeing peeled off the substrate.

BACKGROUND ART

It is widely practiced to attach a label or a sheet printed with productinformation, such as product number and expiration date, to individualproducts for product management or for quality guarantee.

Currently available label printing methods include applying liquid inkusing a printing plate, thermal transfer using ink ribbon, and inkjetprinting. These methods have difficulty, however, in providing a largenumber of products with individually different information.

Hence, patent documents 1 and 2 (see below) propose a laser-markablelaminate comprising a substrate, a base layer, and a hiding layer thatabsorbs laser light to generate heat and ablates. The colors of the baselayer and the hiding layer are combined so that these layers may easilybe visually distinguished. When the laminate is imagewise irradiatedwith a laser beam from the hiding layer side, the irradiated part of thehiding layer is removed to expose the color of the base layer in theform of, for example, letters.

Labels laser-marked with a product serial number and other identifyinginformation are used for certification labeling or approval labeling ofmachines or automobile parts, and the like. When the label is used in,for example, an engine compartment, the use temperature can elevate to50° C. or even higher. Labels, such as certification labels, that areattached to any part of the exterior and interior sides of an automobilecan be subjected to strong direct sunlight or a severe temperatureenvironment in the tropical or desert regions.

When used under such a severe temperature condition, an ordinarylaser-marked label forms a crack or curls, resulting in destructionbefore the expiration of the usable life of the machine or part.

Using an ordinary label as a laminate for laser marking has beenattempted but turned out to be impractical due to poor markability andhandling properties.

It is conceivable to use a commonly employed heat resistant resin, suchas a polyimide resin or a polyamide resin, to make a pigmented resinlayer of a laser-markable laminate. However, most of known heatresistant resins are hard and brittle. For use as a label to be attachedto a curved surface of, e.g., a car body, a motorcycle body, or amachine part, such a resin layer has insufficient flexibility, and thelabel can have its peripheral portion lifted.

The inventors of the present invention proposed in patent document 3(see below) a laser-markable laminate comprising a pigmented resinlayer, a pigmented destructible layer made of a crosslinked acrylicresin and containing a glycol compound, and an adhesive layer. Thelaminate is attachable to a curved surface and is tamper-proof becauseof brittleness. The problem with this laminate is that the laser-markedlaminate (label) has poor workability in attachment to a substrate dueto its softness (lack of moderate stiffness).

-   Patent document 1: JP 09-123606A-   Patent document 2: JP 09-123607A-   Patent document 3: JP 2007-021818A

DISCLOSURE OF THE INVENTION

An object of the invention is to provide a laminate that islaser-markable to create a clearly visible image, does not suffer fromappearance defects, such as a crack, even when exposed to severetemperature conditions as in a desert or tropic region, and has goodworkability in attachment.

Another object of the invention is to provide a laser-markable laminatethat does not suffer from appearance defects, such as a crack, even whensubjected to a severer temperature condition, particularly at 150° C. oreven higher, and has good workability in attachment.

The inventors have found that a laser-markable laminate having enduranceunder high temperature conditions and good attachment workability isobtained by using a crosslinked acrylic resin and balancing thicknessand tensile elongation at break of each layer thereby to improveattachment workability. The invention has been reached based on thesefindings.

The inventors have also found that a laser-markable laminate havingendurance not to suffer from appearance defects, such as a crack, evenunder a high temperature condition of 150° C. or higher and goodattachment workability is obtained by using, as a coloring material, areactive hydroxyl group-containing acrylic resin having a pigmentdispersed therein and providing a structure composed of three layerseach made of a crosslinked acrylic resin composition having a specifichydroxyl value. The invention has been reached based on these findings.

The invention provides in its first aspect a laser-markable, acrylicresin-based laminate including the following resin layers (A1), (B1),and (C1) and having a thickness of 100 to 200 μm.

(A1) A pigmented layer having a thickness of 10 to 30 μm, being made ofan acrylic resin, having a tensile elongation at break of less than 5%,and providing the outermost surface when the laminate is attached to asubstrate.

(B1) A base layer laminated with the pigmented layer, having a thicknessof 30 to 60 μm, providing a visibly distinguishable color differencefrom the pigmented layer (A1), being made of an acrylic resin, andhaving a tensile elongation at break of 15% or more.(C1) A destructible layer laminated with the base layer (B), having athickness of 20 to 150 μm; being made of an acrylic resin, and having atensile elongation at break of less than 10%.

The invention provides in its second aspect a laser-markable, acrylicresin-based laminate including the following resin layers (A2), (B2),and (C2) and having a thickness of 100 to 200 μm.

(A2) A pigmented layer having a thickness of 10 to 30 μm, being made ofan acrylic resin, having a tensile elongation at break of less than 5%,and providing the outermost surface of the laminate when attached to asubstrate.

(B2) A destructible layer laminated with the pigmented layer, having athickness of 30 to 150 μm, providing a visibly distinguishable colordifference from the pigmented layer (A2), being made of an acrylicresin, and having a tensile elongation at break of less than 8%.(C2) A base layer laminated with the destructible layer (B2), having, athickness of 40 to 80 μm, being made of an acrylic resin, and having atensile elongation at break of 12% or more.

The invention provides in its third aspect a laser-markable, acrylicresin-based laminate including the following resin layers (A3), (B3),and (C3) and having a thickness of 100 to 200 μm.

(A3) A pigmented layer being made of a crosslinked acrylic resinobtained by crosslinking an acrylic resin composition with a melaminecrosslinking agent and providing the outermost surface of the laminatewhen attached to a substrate, the acrylic resin composition having ahydroxyl value of 10 to 100 mg KOH/g and containing (A3-1) an acrylicpolymer having a reactive functional group, (A3-2) cellulose acetatebutyrate, and (A3-3) a pigment.(B3) A base layer laminated with the pigmented layer (A3) being made ofa crosslinked acrylic resin obtained by crosslinking an acrylic resincomposition with an isocyanate crosslinking agent and providing avisibly distinguishable color difference from the pigmented layer (A3),the acrylic resin composition having a hydroxyl value of 5 to 30 mgKOH/g or 18 to 40 mg KOH/g and containing (B3-1) an acrylic polymerhaving a reactive functional group, (B3-2) a glycol compound, and (B3-3)a coloring material containing an acrylic resin having a reactivehydroxyl group and a pigment dispersed in the acrylic resin.(C3) A destructible layer laminated with the base layer (B3), being madeof a crosslinked acrylic resin obtained by crosslinking a mixture of anacrylic resin composition and polymer beads with an isocyanatecrosslinking agent, the acrylic resin composition having a hydroxylvalue of 3 to 20 mg KOH/g or 20 to 35 mg KOH/g and containing (C3-1) anacrylic polymer having a reactive functional group, (C3-2) a glycolcompound, and (C3-3) a coloring material containing an acrylic resinhaving a reactive hydroxyl group and a pigment dispersed in the acrylicresin.

The laminate of each of the first and second aspects of the invention isadapted to be irradiated with laser light to have the pigmented layerablated in a desired pattern thereby to visualize the color of the baselayer in the ablated portion. The laminate is thus capable of imagingany desired letters or figures.

The laminate of the third aspect of the invention is usable even underhigh temperature conditions of 150° C. or higher. When it is imagewiseirradiated with laser light, the pigmented layer is ablated to visualizethe color of the base layer in the irradiated portion. The laminate isthus capable of imaging any desired letters or figures.

BRIEF DESCRIPTION OF DRAWING

FIG. 1-1 is a cross-section of a laser-markable brittle laminatetypifying the first aspect of the invention.

FIG. 1-2 is a cross-section of a laser-markable brittle laminateaccording to the first aspect of the invention which contains beads inits destructible layer.

FIG. 2-1 is a cross-section of a laser-markable brittle laminatetypifying the second aspect of the invention.

FIG. 2-2 is a cross-section of a laser-markable brittle laminateaccording to the second aspect of the invention which contains beads inits destructible layer.

FIG. 3 is a cross-section of a laser-markable laminate according to thethird aspect of the invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The laser-markable, acrylic resin-based laminate of the presentinvention will be described in detail with reference to its preferredembodiments.

The laminate of any aspect of the invention has differently coloredlayers including a pigmented layer having laser light absorptivity and abase layer or a destructible layer. The differently colored layers aredesigned such that, when imagewise (for example, in a pattern ofcharacters) irradiated with a focused laser beam with a controlledoutput, the irradiated part of the pigmented layer is removed throughheat generation, followed by melting, and followed by atomization orthrough heat generation, followed by decomposition, and followed byashing whereby the color of the base layer or the destructible layer isexposed to vision.

The laminate of the first aspect of the invention will be describedfirst. The laminate of the first aspect has a pigmented layer (A1) onthe surface thereof. The pigmented layer (A1) is removable onirradiation with laser light. The pigmented layer (A1) is made of apigmented resin that is an acrylic resin having a pigment added theretoand provided by a known method with a prescribed thickness to adjoin abase layer (B1).

The acrylic resin that makes the pigmented layer (A1) is preferably acrosslinked acrylic resin crosslinked with an amino resin crosslinkingagent. As used herein, the term “crosslinked acrylic resin” means anacrylic resin having a functional group crosslinked by using, e.g., acrosslinking agent. As used herein, the term “acrylic resin” refers to aresin consisting mainly of a resin obtained by polymerizing an acrylicmonomer or a methacrylic monomer. The phrase “consist mainly of” as usedherein is intended to mean that the content of the acrylic resin in thetotal resinous component is at least 50%.

Examples of the acrylic monomers include acrylic esters, such as methylacrylate, propyl acrylate, butyl acrylate, 2-hydroxyethyl acrylate, and2-ethylhexyl acrylate. Examples of the methacrylic monomers includemethyl methacrylate, ethyl methacrylate, propyl methacrylate, butylmethacrylate, and ethylene glycol dimethacrylate. Examples of thefunctional group include a hydroxyl group, a mercapto group, an epoxygroup, an amide group, and a methylolated acrylamide group.

Preferred acrylic resins are copolymers obtained from a monomer having ahydroxyl group as a functional group in view of pot life after mixingwith a crosslinking agent and controllability of tensile elongation atbreak after crosslinking. Copolymers obtained from methyl methacrylate(MMA) is also suitable in view of the hardness after crosslinking.

An amino resin crosslinking agent is used as the crosslinking agent ofthe pigmented layer (A1). Examples of the amino resin crosslinking agentinclude a melamine crosslinking agent, a guanamine crosslinking agent,and a urea crosslinking agent. The melamine crosslinking agent ispreferred in terms of controlling physical properties, such as heatresistance and tensile elongation at break after crosslinking.

The crosslinking agent is used in an amount of 0.5 to 1.5 equivalentweights, preferably 0.8 to 1.2 equivalent weights, per equivalent weightof the reactive functional group of the acrylic resin.

The pigmented layer (A1) has a thickness of 10 to 30 μm, preferably 10to 20 μm. A thickness of 10 μm or more assures sufficient hidingproperties. A thickness less than 30 μm assures complete removal of theirradiated part on laser light irradiation.

It is recommended for the pigmented layer (A1) to have a pigment contentof 1% to 300%, preferably 5% to 250%, more preferably 8% to 200%, byweight. When the pigment content is less than 1 wt %, the pigmentedlayer (A1) generally has low hiding ability only to provide a smallcontrast to the background color. With a pigment content of 300 wt % ormore, the pigmented layer would be too brittle and can form a crack whenthe laminate is attached to a curved surface.

The pigments that can be used in the pigmented layer (A1) and a baselayer (B1) and a destructible layer (C1) hereinafter described are notparticularly limited but are preferably those having weatherability andendurance during long use as well as removability by irradiation withlaser light. Specifically, suitable pigments may be chosen from thosedescribed in Colour Index 3rd Edition, The Society of Dears andColourist (1971) and its Supplements (1975). The pigment nameshereinafter recited are in accordance with ibid, “Colour Index GenericName”. For instance, Bk-1 denotes C.I. Pigment Black 1; Bk representsblack; and W represents white.

While the pigments may have any color, including yellow, orange, red,purple, blue, green, brown, black, or white, a black and a white pigmentare usually used. Preferred pigments are described below.

The black pigments may be organic or inorganic. Examples of preferredorganic black pigments include aniline black (Bk-1) and perylene black(Bk-31).

Examples of preferred inorganic black pigments include carbon black(Bk-31), carbon black (Bk-7), carbon black (Bk-9), iron black (Bk-11),and cobalt oxide pigment (Bk-13).

Preferred of these pigments are amorphous or graphite carbon black(black). Carbon black pigments preferably have an average particle sizeof 10 to 500 nm, more preferably 15 to 120 nm. Various commerciallyavailable carbon black products with small average particle sizes areusable.

The white pigments are preferably inorganic ones, such as zinc white(W-4), zinc sulfide (W-7), titanium dioxide (W-6), calcium carbonate(W-18), clay (W-19), barium sulfate (W-21), alumina white (W-24), silica(W-27), muscovite (W-20), and talc (W-26).

Preferred of the pigments is rutile titanium oxide (white). Titaniumoxide to be used preferably has an average particle size of 10 to 500nm, more preferably 20 to 100 nm. Various commercially availabletitanium oxide products with small average particle sizes are usable.

The pigmented layer (A1) may contain mica or aluminum powder in additionto the pigment in an amount that does not affect the pigmentation andweatherability of the layer.

Carbon black or titanium oxide used as a pigment in the pigmented layer(A1) is capable of converting laser light to heat. In the case of usinga pigment that does not absorb laser light, a compound capable ofconverting laser light to heat is needed in some cases. In such cases,two or more pigments may be used in combination, or one or more than onepigment may be used in combination with at least one compound capable ofconverting laser light to heat.

Examples of the compound capable of converting laser light to heatinclude carbon black and cyanine, phthalocyanine or inorganic infraredabsorbers.

The laminate of the first aspect of the invention further includes abase layer (B1) laminated with the pigmented layer (A1). The base layer(B1) is made of a crosslinked acrylic resin and provides a visiblydistinguishable color difference from the pigmented layer (A1). The baselayer (B1) is preferably made of a crosslinked acrylic resin. While theacrylic resin making the base layer (B1) is chosen from the samematerials usable to make the pigmented layer (A1), the base layer (B1)is different from the pigmented layer (A1) in kind of crosslinking agentor additive so as to have flexibility represented by a tensileelongation at break of 15% or more.

The crosslinking agent used to crosslink the acrylic resin of the baselayer (B1) is preferably an isocyanate crosslinking agent, particularlyan aliphatic or alicyclic isocyanate crosslinking agent, in view offlexibility after crosslinking. Examples of the aliphatic or alicyclicisocyanate crosslinking agent include trans-cyclohexane1,4-diisocyanate, pentamethylene diisocyanate, hexamethylenediisocyanate, heptamethylene diisocyanate, 4,4′-dicyclohexylbutanediisocyanate, lysine diisocyanate, isophorone diisocyanate, lysine estertriisocyanate, 1,6,11-undecatriisocyanate, 1,8-diisocyanate 4-isocyanatemethyloctane, 1,3,6-hexamethylene triisocyanate, bicycloheptanetriisocyanate, and trimethylhexamethylene diisocyanate.

The crosslinking agent is used in an amount of 0.1 to 1.3 equivalentweights, preferably 0.2 to 1.0 equivalent weight, per equivalent weightof the functional group of the resin making the base layer (B1). Toolarge an amount of the crosslinking agent results in reducedflexibility. Too small an amount of the crosslinking agent results inreduced heat resistance and durability.

The base layer (B1) has a color visibly distinguishable from thepigmented layer (A1). The pigments to be used in the base layer (B1) maybe selected from those useful in the pigmented layer (A1). A recommendedpigment content in the base layer (B1) is 10% to 500%, preferably 30% to300%, more preferably 40% to 250%, by weight. A pigment content lessthan 10 wt % is unable to assure hiding properties. A pigment content of500 wt % or more results in a failure to maintain a film form.

The base layer (B1) may contain a glycol compound as a flexibilityimparting agent to retain the flexibility. The term “glycol compound” asused herein is intended to mean a condensation product of a diol.Examples of the glycol compound include ethylene glycol, propyleneglycol, 1,4-butanediol, diethylene glycol, and glycol polymers, such aspolyethylene glycol, poly(tetramethyl glycol), and a THF-neopentylglycol copolymer. The glycol polymers are preferred in terms ofvolatility, performance of imparting flexibility per unit amount ofaddition, and water resistance. Poly(tetramethyl glycol) is particularlypreferred in terms of versatility and cost.

The glycol compound may be used in an amount of 1% to 10%, preferably 2%to 8%, more preferably 3% to 6%, by weight based on the resincomposition. With a glycol compound content of 1 wt % or less, the filmcan form a crack on bending in attachment. With a glycol compoundcontent of 10 wt % or more, the laminate (e.g., a label) once attachedis able to be stripped off without breakage.

The base layer (B1) has a thickness of 30 to 60 μm, preferably 40 to 50μm.

The laminate of the first aspect further includes a destructible layer(C1) that is made of an acrylic resin and laminated with the base layer(B1). The destructible layer (C1) is preferably made of a crosslinkedacrylic resin. The acrylic resin may be chosen from those usable to makethe pigmented layer (A1). The destructible layer (C1) is formed of aresin rendered friable or brittle by crosslinking or addition of abrittleness-imparting component described hereunder. The destructiblelayer (C1) should have a tensile elongation at break of less than 10%.

Examples of the crosslinking agent usable to crosslink the acrylic resinof the destructible layer (C1) include melamine crosslinking agents,isocyanate crosslinking agents, epoxy crosslinking agents, polyaminecrosslinking agents, and aldehyde crosslinking agents. It is preferredto use a melamine crosslinking agent or an isocyanate crosslinking agentwithin a range that satisfies the aforementioned requirement of tensileelongation at break, with controlling physical properties, such as heatresistance and hardness after crosslinking, taken into consideration.

The melamine crosslinking agent usable in the pigmented layer (A1) orthe isocyanate crosslinking agent usable in the base layer (B1) mayappropriately be used in the destructible layer (C1) in a range suchthat the above recited requirement of tensile elongation at break may besatisfied:

The crosslinking agent is used in an amount of 0.1 to 1.5 equivalentweights, preferably 0.2 to 1.3 equivalent weights, more preferably 0.3to 1.2 equivalent weights, per equivalent weight of the functional groupof the resin of the destructible layer (C1). Using too much crosslinkingagent makes the layer too brittle, which may impair the workability ofthe laminate. Too low an amount of the crosslinking agent makes thelayer hardly destructible.

It is preferred for the destructible layer (C1) to contain a brittlenessimparting component. Examples of useful brittleness imparting componentinclude inorganic particles, such as glass beads, silica particles, andcalcium carbonate particles, and organic particles, such as acrylicbeads, styrene beads, and silicone beads. Preferred of them are glassbeads, acrylic beads, styrene beads, and silicone beads in terms ofreachable narrowness of particle size distribution. Glass beads andacrylic beads are more preferred.

The organic or inorganic particles that are added as a brittlenessimparting component must have an average particle size not greater thanthe thickness of the destructible layer. The average particle size ofthe brittleness imparting component ranges from 1 to 150 μm, preferably5 to 100 μm, more preferably 10 to 80 μm. With the particle size of 1 μmor less, brittleness is not imparted. With the particle size of 150 μmor more, the layer easily forms a crack in the attachment operation.

The content of the brittleness imparting component is 10% to 280%,preferably 10% to 200%, more preferably 30% to 100%, by volume based onthe resin of the destructible layer (C1). Addition of 10% or less byvolume of the brittleness imparting component produces no effect.Addition of 280% or more by volume of the brittleness impartingcomponent results in void formation between the particles, which cancause cracking during attachment.

The destructible layer (C1) may be colored and may be transparent. Wherecolored, the destructible layer (C1) is colored preferably in the samehue as the base layer (B1). The same pigments (colorant) usable in thepigmented layer (A1) may be used. The recommended pigment content in thedestructible layer (C1) is 10% to 500%, preferably 30% to 300%, morepreferably 50% to 250%, by weight. A pigment content of less than 10 wt% is unable to assure hiding properties. A pigment content of 500 wt %or more results in a failure to maintain a film form.

The laminate of the first aspect is required to have a tensileelongation at break of 5% to 30% measured in accordance with JIS K7127.The tensile elongation at break is preferably 10% to 25%. A tensileelongation at break of at least 5% assures workability. A tensileelongation at break of less than 30% secures non-reusability of thelabel.

The laminate of the first aspect has a tensile strength of at least 20N/10 mm, preferably 25 N/10 mm or more, measured in accordance with JISK7127. A label formed of the laminate with a tensile strength of lessthan 20 N/10 mm has poor workability in attachment due to lack ofstiffness.

When a label having the laminate of the first aspect is attached to asubstrate and peeled off by the hand or with a tool, the film isdestroyed. Destruction occurs through various mechanisms. In frequentcases, the pigmented layer (A1) with a small tensile breaking strengthunrecoverably undergoes cracking due to the strain caused by the stressaccompanying peeling. Known brittle laminates designed to be destroyedwhen peeled are so hard and brittle that they have poor workability orpoor conformability to the contour of a substrate when attached as alabel. In contrast, the laminate of the first aspect exhibits bothworkability and destructibility because a resin layer with a largetensile breaking strength is provided as the base layer (B1) and thethree layers have respectively selected thicknesses.

The laminate of the first aspect may further include an adhesive layerwith which it is attached to a substrate. The adhesive layer has athickness of 15 to 100 μm, preferably 20 to 70 μm, more preferably 25 to45 μm. A thickness of 15 μm or more assures sufficient adhesion to asubstrate. A thickness of less than 100 μm is suitable for theattachment and economically advantageous.

The resin making the adhesive layer is not limited. However, an acrylicadhesive is preferably used in view of weatherability, transparency, andanti-yellowing properties. If desired, the acrylic resin adhesive maycontain additives, such as a tackifier, a UV absorber, a photostabilizer, and an antioxidant.

The laminate of the first aspect is prepared by coating, or printing(e.g. gravure printing) a pigmented layer-forming resin having a pigmentdispersed therein to a carrier film, drying the resin applied to form apigmented layer (A1), coating, or printing (e.g., gravure printing) abase layer-forming resin having a pigment dispersed therein to thepigmented layer (A1), drying the resin applied to form a base layer(B1), coating, or printing (e.g., gravure printing) a destructiblelayer-forming resin having a pigment dispersed therein to the base layer(B1), and drying the resin applied to form a destructible layer (C1).The laminate may be otherwise prepared using known methods for producinga laminate film, for example a method including forming pigmented dryfilms corresponding to the layers (A1), (B1), and (C1) and laminatingthe dry films by thermopress bonding or with an adhesive or acombination of these methods.

As illustrated in FIG. 1-1, the laminate of the first aspect includes anadhesive layer 4, (C1) a destructible layer 3 that is destroyed onpeeling the laminate, (B1) a base layer 2, and (A1) a pigmented layer 1that is destroyed on peeling the laminate and ablated on irradiationwith laser light, being stacked one on top of another in the ordernamed. On imagewise irradiating the laminate with laser light, the (A1)pigmented layer 1 and part of the (B1) base layer 2 are removed in thepattern of laser irradiation to expose the (B1) base layer 2. As aresult, a desired image appears on the laminate as a color contrastbetween the (A1) pigmented layer 1 and the (B1) base layer 2. The (C1)destructible layer may contain beads 5 as a brittleness impartingcomponent, which embodiment is illustrated in FIG. 1-2.

Lasers used for irradiation include CO₂ lasers, Nd:YAG lasers, excimerlasers, semiconductor lasers, semiconductor excited solid state lasers.Ar lasers, N₂/dye lasers, and HeCd lasers. CO₂ lasers, Nd:YAG lasers,and so on that are inexpensive and relatively easy to operate aregenerally used.

The laminate according to the second aspect of the invention will thenbe described. The description of the first aspect applies to the secondaspect with the exceptions noted hereafter.

The laminate of the second aspect has a pigmented layer (A2) on thesurface thereof. The pigmented layer (A2) is removable on irradiationwith laser light. The pigmented layer (A2) is made of a pigmented resinthat is an acrylic resin having a pigment added thereto and providedwith a prescribed thickness by a known method to adjoin a destructiblelayer (B2).

The acrylic resin that can be used to make the pigmented layer (A2) ispreferably a crosslinked acrylic resin crosslinked with an amino resincrosslinking agent similarly to the pigmented layer (A1) of the laminateof the first aspect. As used herein, the term “acrylic resin” means aresin consisting mainly of a resin obtained by polymerizing an acrylicmonomer or a methacrylic monomer. The phrase “consist mainly of” as usedherein is intended to mean that the content of the acrylic resin in thetotal resinous component is at least 50%.

Examples of the acrylic monomer, the methacrylic monomer, and thereactive functional group include those recited above with respect tothe pigmented layer (A1) of the first aspect.

Preferred resins are copolymers obtained from a monomer having ahydroxyl group as a functional group in view of pot life after mixingwith a crosslinking agent and controllability of tensile elongation atbreak after crosslinking. Copolymers obtained from methyl methacrylate(MMA) is also suitable in view of the hardness after crosslinking.

Similarly to the pigmented layer (A1) of the laminate of the firstaspect, an amino resin crosslinking agent is used as the crosslinkingagent of the pigmented layer (A2). Examples of the amino resincrosslinking agent include a melamine crosslinking agent, a guanaminecrosslinking agent, and a urea crosslinking agent. The melaminecrosslinking agent is preferred in terms of controlling physicalproperties, such as heat resistance and tensile elongation at breakafter crosslinking.

The crosslinking agent is used in an amount of 0.5 to 1.5 equivalentweights, preferably 0.8 to 1.2 equivalent weights, per equivalent weightof the reactive functional group of the resin.

The thickness of the pigmented layer (A2) is 10 to 30 μm, preferably 10to 20 μm, similarly to the pigmented layer (A1) of the first aspect.With a thickness of 10 μm or more, sufficient hiding properties areobtained. A thickness of less than 30 μm assures complete removal of theirradiated part on irradiation with a laser beam.

It is recommended for the pigmented layer (A2) to have a pigment contentof 1% to 300%, preferably 5% to 250%, more preferably 8% to 200%, byweight. When the pigment content is less than 1 wt %, the pigmentedlayer (A2) generally has low hiding ability only to provide a smallcontrast to the background color. With a pigment content of 300 wt % ormore, the pigmented layer would be too brittle and can form a crack whenthe laminate is attached to a curved surface.

Similarly to the pigmented layer (A1) of the first aspect, the pigmentsthat can be used in the pigmented layer (A2) and a base layer (C2) and adestructible layer (B2) hereinafter described are preferably thosehaving weatherability and endurance during long use as well asremovability by irradiation with laser light. Specifically, suitablepigments may be chosen from those described in Colour Index 3rd Edition,The Society of Dears and Colourist (1971) and its Supplements (1975).The pigment names hereinafter recited are in accordance with ibid.“Colour Index Generic Name”. For instance, Bk-1 denotes C.I. PigmentBlack 1; Bk represents black; and W represents white.

Similarly to the pigmented layer (A1) of the first aspect, while thepigments may have any color, including yellow, orange, red, purple,blue, green, brown, black, or white, black and white pigments areusually used. Preferred pigments are described below.

Preferred black pigments for use in the second aspect are the same asthose recited above with respect to the pigmented layer (A1) of thefirst aspect.

Preferred white pigments for use in the second aspect are the same asthose recited above with respect to the pigmented layer (A1) of thefirst aspect.

Similarly to the pigmented layer (A1) of the first aspect, preferred ofthe pigments is rutile titanium oxide (white). Titanium oxide to be usedpreferably has an average particle size of 10 to 500 nm, more preferably20 to 100 nm. Various commercially available titanium oxide productswith small average particle sizes are usable.

The pigmented layer (A2) may contain mica or aluminum powder in additionto the pigment in an amount that does not affect the pigmentation andweatherability of the layer.

Carbon black or titanium oxide used as a pigment in the pigmented layer(A2) is capable of converting laser light to heat. In the case of usinga pigment that does not absorb laser light, a compound capable ofconverting laser light to heat is needed in some cases. In such cases,two or more pigments may be used in combination, or one or more than onepigment may be used in combination with at least one compound capable ofconverting laser light to heat.

Examples of the compound capable of converting laser light to heatinclude carbon black and cyanine, phthalocyanine or inorganic infraredabsorbers.

The laminate of the second aspect further includes a destructible layer(B2) that is made of an acrylic resin and laminated with the pigmentedlayer (A2). The destructible layer (B2) is preferably made of acrosslinked acrylic resin. The acrylic resin is chosen from the samematerials usable to make the pigmented layer (A2). It is necessary thatthe destructible layer (B2) be made of a resin endowed with brittlenessby crosslinking or addition of a brittleness imparting componenthereinafter described and have a tensile elongation at break of lessthan 8%.

Examples of the crosslinking agent usable to crosslink the acrylic resinof the destructible layer (B2) include those described with respect tothe destructible layer (C1) of the first aspect, i.e., melaminecrosslinking agents, isocyanate crosslinking agents, epoxy crosslinkingagents, polyamine crosslinking agents, and aldehyde crosslinking agents.It is preferred to use a melamine crosslinking agent or an isocyanatecrosslinking agent within a range that satisfies the aforementionedrequirement of tensile elongation at break, with physical properties,such as heat resistance and hardness after crosslinking, taken intoconsideration.

The melamine crosslinking agent usable in the pigmented layer (A2) andan isocyanate crosslinking agent usable in a base layer (C2) hereinafterdescribed may be used appropriately in the destructible layer (B2) in arange such that the above recited requirement of tensile elongation atbreak may be satisfied.

The crosslinking agent is used in an amount of 0.1 to 1.5 equivalentweights, preferably 0.2 to 1.3 equivalent weights, more preferably 0.3to 1.2 equivalent weights, per equivalent weight of the functional groupof the resin of the destructible layer (B2) similarly to thedestructible layer (C1) of the first aspect. Using too much crosslinkingagent makes the layer too brittle, which may impair the workability ofthe laminate. Too low an amount of the crosslinking agent makes thelayer hardly destructible.

The destructible layer (B2) may contain a brittleness impartingcomponent. Examples of useful brittleness imparting components are thesame as those recited above with respect to the destructive layer (C1)of the first aspect.

The organic or inorganic particles that may be added as a brittlenessimparting component must have an average particle size not greater thanthe thickness of the destructible layer similarly to the destructiblelayer (C1) of the first aspect. The average particle size of thebrittleness imparting component ranges from 1 to 150 μm, preferably 5 to100 μm, more preferably 10 to 80 μm. With the particle size being 1 μmor less, brittleness is not imparted. With the particle size of 150 μmor more, the layer easily forms a crack in the attachment operation.

Similarly to the destructible layer (C1) of the first aspect, thecontent of the brittleness imparting component is 10% to 280%,preferably 10% to 200%, more preferably 30% to 100%, by volume based onthe resin of the destructible layer (B2). Addition of 10% or less byvolume of the brittleness imparting component produces no effect.Addition of 280% or more by volume of the brittleness impartingcomponent results in void formation between the particles, which cancause cracking during attachment.

The destructible layer (B2) should be pigmented so as to provide avisually distinguishable color difference from the pigmented layer (A2).Pigmentation of the destructible layer (B2) may be achieved using any ofthe pigments (colorants) usable in the pigmented layer (A2). Similarlyto the destructible layer (C1) of the first aspect, the recommendedpigment content in the destructible layer (B2) is 10% to 500%,preferably 30% to 300%, more preferably 50% to 250%, by weight. Apigment content of less than 10 wt % is unable to assure hidingproperties. A pigment content of 500 wt % or more results in a failureto maintain a film form.

The laminate of the second aspect further includes a base layer (C2)made of an acrylic resin and laminated with the destructible layer (B2).The base layer (C2) may be colored and may be transparent. Wherecolored, the base layer (C2) is colored preferably in the same hue asthe destructible layer (B2). The same pigments usable in the pigmentedlayer (A2) may be used. While the acrylic resin making the base layer(C2) may be selected from the resins usable in the pigmented layer (A2),the base layer (C2) is different from the pigmented layer (A2) in kindof crosslinking agent or additive so as to have flexibility representedby a tensile elongation at break of 12% or more.

Similarly to the pigmented layer (B1) of the first aspect, thecrosslinking agent used to crosslink the acrylic resin of the base layer(C2) is preferably an isocyanate crosslinking agent, particularly analiphatic or alicyclic isocyanate crosslinking agent, in view offlexibility after crosslinking. Examples of the aliphatic or alicyclicisocyanate crosslinking agent include those enumerated above withrespect to the base layer (B1) of the first aspect of the invention.

Similarly to the base layer (B1) of the first aspect, the crosslinkingagent is used in an amount of 0.1 to 1.3 equivalent weights, preferably0.2 to 1.0 equivalent weight, per equivalent weight of the functionalgroup of the resin making the destructible layer (B2). Too large anamount of the crosslinking agent results in reduced flexibility. Toosmall an amount of the crosslinking agent results in reduced heatresistance and durability.

The base layer (C2) may be colored and may be transparent. Wherecolored, the base layer (C2) is colored preferably in the same hue asthe destructible layer (B2). The same pigments usable in the pigmentedlayer (A2) may be used. Similarly to the base layer (B1) of the firstaspect, a recommended pigment content in the base layer (C2) is 10% to500%, preferably 30% to 300%, more preferably 50% to 250%, by weight. Apigment content of less than 10 wt % is unable to assure hidingproperties. A pigment content of 500 wt % or more results in a failureto maintain a film form.

The base layer (C2) may contain the same glycol compound as usable inthe base layer (B1) of the first aspect as a flexibility imparting agentto retain the flexibility. Examples of the glycol compound include thoseenumerated above with respect to the base layer (B1) of the firstaspect. The glycol polymers are preferred in terms of volatility,performance of imparting flexibility per unit amount of addition, andwater resistance. Poly(tetramethyl glycol) is particularly preferred interms of versatility and cost.

Similarly to the base layer (B1) of the first aspect, the glycolcompound may be used in an amount of 1% to 10%, preferably 2% to 8%,more preferably 3% to 6%, by weight based on the resin composition. Witha glycol compound content of 1 wt % or less, the film can form a crackon bending in attachment. With a glycol compound content of more than 10wt % or more, the laminate once attached may be peeled off withoutdamage.

The base layer (C2) has a thickness of 40 to 80 μm, preferably 50 to 60μm. The base layer (C2) with a thickness of at least 40 mμ provides thelaminate with sufficient flexibility. With a thickness of less than 80μm, the base layer (C2) exhibits destructibility.

The laminate of the second aspect should have a tensile elongation atbreak of 5% to 30% measured in accordance with JIS K7127. The tensileelongation at break is preferably 10% to 25%. A tensile elongation atbreak of at least 5% assures workability. A tensile elongation at breakof less than 30% secures non-reusability.

The laminate of the second aspect has a tensile strength of at least 25N/10 mm, preferably 30 N/10 mm or more, measured in accordance with JISK7127. A label formed of the laminate with a tensile strength of lessthan 25 N/10 mm has poor workability in attachment due to lack ofstiffness.

Similarly to the label having the laminate of the first aspect, when alabel having the laminate of the second aspect attached to a substrateand peeled off by the hand or with a tool, the film is destroyed.Destruction occurs through various mechanisms. In frequent cases, thepigmented layer (A2) with a small tensile breaking strengthunrecoverably undergoes cracking on peeling. Known brittle laminatesdesigned to be destroyed when peeled are so hard and brittle that theyhave poor workability or poor conformability to the contour of asubstrate when attached to a substrate as a label. In contrast, thelaminate of the invention exhibits both workability and destructibilitybecause a resin layer with a large tensile breaking, strength isprovided as the base layer (C2) and the three layers have respectivelyselected thicknesses.

Similarly to the laminate of the first aspect, the laminate of thesecond aspect may further include an adhesive layer with which it isattached to a substrate. Similarly to the adhesive layer of the laminateaccording to the first aspect, the adhesive layer has a thickness of 15to 100 μm, preferably 20 to 70 μm, more preferably 25 to 45 μm. With athickness of 15 μm or more, the laminate attached to a substrate comesoff, which provides the substrate with good processability in, forexample, bending. A thickness of less than 100 μm is suitable for theattachment and economically advantageous.

Similarly to the adhesive layer of the laminate of the first aspect, theadhesive layer is preferably made of an acrylic adhesive in view ofweatherability, transparency, and anti-yellowing properties. If desired,the acrylic adhesive may contain additives, such as a tackifier, a UVabsorber, a photo stabilizer, and an antioxidant.

The laminate of the second aspect is prepared by coating, or printing(e.g., gravure printing) a pigmented layer-forming resin having apigment dispersed therein to a carrier film, drying the resin applied toform a pigmented layer (A2), coating, or printing, (e.g. gravureprinting) a destructible layer-forming resin to the pigmented layer(A2), drying the resin applied to form a destructible layer (B2),coating, or printing (e.g., gravure printing) a base layer-forming resinhaving a pigment dispersed therein to the destructible layer (B2), anddrying the resin applied to form a base layer (C2). The laminate may beotherwise prepared using known methods for producing a laminate film,for example a method including forming pigmented dry films correspondingto the layers and laminating the dry films by thermopress bonding orwith an adhesive or a combination of these methods.

As illustrated in FIG. 2-1, the laminate of the second aspect includesan adhesive layer 4, (C2) a base layer 2, (B2) a destructible layer 3that is destroyed on peeling the laminate, and (A2) a pigmented layer 1that is laser ablatable, being stacked one on top of another in theorder named. On imagewise irradiating the laminate with laser light, the(A2) pigmented layer 1 is ablated in the pattern of laser irradiation toexpose the (B2) destructible layer 3. As a result, a desired imageappears on the laminate as a color contrast between the (A2) pigmentedlayer 1 and the (B2) destructible layer 3. The (B2) destructible layer 3may contain beads 5 as a brittleness imparting component, whichembodiment is illustrated in FIG. 2-2.

Examples of lasers used for laser ablation include those listed abovewith respect to the first aspect. CO₂ lasers, Nd:YAG lasers, and so onthat are inexpensive and relatively easy to operate are generally used.

The laminate according to the third aspect of the invention will now bedescribed. The description of the first and second aspects applies tothe third aspect with the exceptions noted hereafter.

The laminate of the third aspect has a pigmented layer (A3) on thesurface thereof. The pigmented layer (A3) is ablatable on irradiationwith laser light. The pigmented layer (A3) is made of a pigmented resinthat is an acrylic resin having a pigment added thereto and providedwith a prescribed thickness by lamination or coating in a known mannerto adjoin a base layer (B3).

The resin that can be used to make the pigmented layer (A3) is acrosslinked acrylic resin obtained by crosslinking an acrylic resincomposition with a melamine crosslinking agent. The acrylic resincomposition contains (A3-1) an acrylic polymer having a reactivefunctional group, (A3-2) cellulose acetate butyrate (CAB), and (A3-3) apigment.

As used herein, the term “acrylic polymer having a reactive functionalgroup” means a resin consisting mainly of a resin obtained bypolymerizing an acrylic monomer or a methacrylic monomer. The term“reactive functional group” means a functional group reactive with acrosslinking aunt, such as a hydroxyl group or a carboxyl group. Thephrase “consist mainly of” as used herein is intended to mean that thecontent of the acrylic resin in the total resinous component is at least50%.

Examples of the acrylic monomer, the methacrylic monomer, and thereactive functional group include those recited above with respect tothe pigmented layer (A1) of the laminate of the first aspect.

Of the resin recited, preferred are copolymers obtained from a monomerhaving a hydroxyl group as a reactive functional group, such as2-hydroxyethyl acrylate, in view of pot life after mixing with acrosslinking agent and controllability of tensile elongation at breakafter crosslinking.

The pigmented layer (A3) contains cellulose acetate butyrate (CAB) toassure processability and control the brittleness of the pigmented layer(A3). The amount of CAB is 0.5% to 10%, preferably 1% to 8%, by weight.

The pigmented layer (A3) contains 1% to 10% by weight, preferably 2% to8% by weight, of a pigment (colorant). When the pigment content is lessthan 1 wt %, the pigmented layer generally has low hiding ability onlyto provide a small contrast to the background color. With a pigmentcontent of 10 wt % or more, the pigmented layer (A3) would be toobrittle and can form a crack when the laminate is attached to a curvedsurface.

Similarly to the pigmented layer (A1) of the first aspect, the pigments(colorants) that can be used in the pigmented layer (A3) and a baselayer (B3) and a destructible layer (C3) hereinafter described arepreferably those having weatherability and endurance during lone use aswell as removability by irradiation with laser light.

Similarly to the first aspect, while the pigments may have any color,including yellow, orange, red, purple, blue, green, brown, black, orwhite, black pigments and white pigments are usually used. Preferredpigments are described below.

Preferred black pigments for use in the third aspect are the same asthose recited above as preferred black pigments for use in the pigmentedlayer (A) of the first aspect.

Similarly to the pigmented layer (A1) of the first aspect, preferred ofthe black pigments are amorphous or graphite carbon black (black).Carbon black pigments preferably have an average particle size of 10 to500 nm, more preferably 15 to 120 nm. Various commercially availablecarbon black products with small average particle sizes are usable.

Preferred white pigments are the same as those recited above aspreferred white pigments for use in the pigmented layer (A1) of thefirst aspect.

Similarly to the pigmented layer (A1) of the first aspect, preferred ofthe pigments is rutile titanium oxide (white). Titanium oxide to be usedpreferably has an average particle size of 10 to 500 nm, more preferably20 to 100 nm. Various commercially available titanium oxide productswith small average particle sizes are usable.

The pigmented layer (A3) may contain mica or aluminum powder in additionto the pigment in an amount that does not affect the pigmentation andweatherability of the layer.

Carbon black or titanium oxide used as a pigment in the pigmented layer(A3) is capable of converting laser light to heat. In the case of usinga pigment that does not absorb laser light, a compound capable ofconverting laser light to heat is needed in some cases. In such cases,two or more pigments may be used in combination, or one or more than onepigment may be used in combination with at least one compound capable ofconverting laser light to heat.

Examples of the compound capable of converting laser light to heatinclude carbon black and cyanine, phthalocyanine or inorganic infraredabsorbers.

The acrylic resin composition used to make the pigmented layer (A3) hasa hydroxyl value of 10 to 100 mg KOH/g, preferably 30 to 80 mg KOH/g. Asused herein, the term “hydroxyl value” is equivalent to mean the numberof functional groups. With a hydroxyl value of at least 10 mg KOH/g, theresin composition acquires sufficient heat resistance and brittleness oncrosslinking. With a hydroxyl value less than 100 mg KOH/g, workabilityis secured.

A melamine crosslinking agent is used to make the pigmented layer (A3)in terms of controlling physical properties, such as heat resistance andtensile elongation at break after crosslinking.

The crosslinking agent is used in an amount of 1.0 to 2.0 equivalentweights, preferably 1.1 to 1.5 equivalent weights, per equivalent weightof the hydroxyl group calculated from the hydroxyl value of the resin.Too low an amount of the crosslinking agent results in poor heatresistance and insufficient brittleness of the pigmented layer (A3).Using too much crosslinking agent makes the layer too brittle, which mayimpair the workability of the laminate.

The thickness of the pigmented layer (A3) is 10 to 30 μm, preferably 10to 20 μm. With a thickness of 10 μm or more, sufficient hidingproperties are obtained. A thickness of less than 30 μm assures completeremoval of the irradiated part on irradiation with a laser beam.

The laminate of the third aspect includes a base layer (B3) laminatedwith the pigmented layer (A3) and providing a visibly distinguishablecolor difference from the pigmented layer (A3). The base layer (B3) ismade of a crosslinked acrylic resin obtained by crosslinking an acrylicresin composition with an isocyanate crosslinking agent. The acrylicresin composition has a hydroxyl value of 18 to 40 mg KOH/g, preferably18 to 35 mg KOH/g. The acrylic resin composition includes (B3-1) anacrylic polymer having a reactive functional group, (B3-2) a glycolcompound, and (B3-3) a coloring material containing an acrylic resinhaving a reactive hydroxyl group (reactive with the isocyanatecrosslinking agent) and a pigment dispersed in the acrylic resin.

The acrylic polymer (B3-1) having a reactive functional group for use inthe base layer (B3) may be selected from the same resins as used to makethe pigmented layer (A3).

The base layer (B3) may contain the same glycol compound as used in thebase layer (B1) of the first aspect as a flexibility imparting agent toretain the flexibility. Examples of the glycol compound include thoseenumerated above with respect to the base layer (B1) of the firstaspect. The glycol polymers are preferred in terms of volatility,performance of imparting flexibility per unit amount of addition, andwater resistance. Poly(tetramethyl glycol) is particularly preferred interms of versatility and cost.

The glycol compound may be used in an amount of 1% to 10%, preferably 2%to 8%, more preferably 3% to 6%, by weight based on the total solidscontent of the base layer (B3). i.e., the solid content of the pigmentand the resin of the base layer. With a glycol compound content of 1 wt% or less, the film can form a crack on bending in attachment. With aglycol compound content of 10 wt % or more, the laminate (e.g., a label)once attached to a substrate may be reusably strippable without damage.

The base layer (B3) is pigmented in a color that contrasts with thepigmented layer (A3). An acrylic resin containing a reactive hydroxylgroup having a pigment dispersed therein is used as a coloring material.By using an acrylic resin containing a reactive hydroxyl group having apigment dispersed therein as a coloring material, a laminate having bothheat resistance and attachment workability is obtained.

The acrylic resin having a reactive hydroxyl group that can be used hereis prepared by copolymerizing an acrylic monomer having a reactivehydroxyl group and other acrylic monomer(s).

A recommended proportion of the component derived from the acrylicmonomer having a reactive hydroxyl group in the copolymer is usually 3%to 20%, preferably 6% to 15%, by weight. As long as the proportion doesnot exceed the upper limit, flexibility is secured. As long as theproportion is at least the lower limit, flow in a high temperatureenvironment can be controlled.

Examples of the hydroxyl-containing acrylic monomer include2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropylacrylate, 4-hydroxybutyl acrylate, polyethylene glycol monoacrylate,5-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate,3-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, polyethyleneglycol monomethacrylate, allyl alcohol, and methallyl alcohol. Preferredof them are 2-hydroxyethyl acrylate and 2-hydroxypropyl acrylate interms of copolymerizability with other acrylic monomer(s). Particularlypreferred of them is 2-hydroxyethyl acrylate. These hydroxyl-containingacrylic monomers may be used either individually or as a combination oftwo or more thereof.

The pigment that is dispersed in the acrylic resin having a reactivehydroxyl group to provide a coloring material for use in the base layer(B3) is chosen from those described above for use in the pigmented layer(A3).

Preferred of the pigments is rutile titanium oxide (white). Titaniumoxide to be used preferably has an average particle size of 10 to 500nm, more preferably 20 to 100 nm. Various commercially availabletitanium oxide products with small average particle sizes are usable.

The pigment may be dispersed in the acrylic resin having a reactivehydroxyl group by any method. In view of operation convenience, ordinarystirrers, such as a disper stirrer and a stirring blade, may be used.The coloring material may have the pigment dispersed in an amount of 10to 400%, preferably 20 to 200%, by weight based on the acrylic resin.

A recommended pigment content in the base layer (B3) is 20% to 120%,preferably 30% to 100%, by weight. A pigment content less than 20 wt %results in insufficient hiding properties. When the amount of thepigment is 120 wt % or more, dispersibility tends to reduce.

The acrylic resin composition used to make the base layer (B3) has ahydroxyl value of 18 to 40 mg KOH/g, preferably 18 to 35 mg KOH/g.

The crosslinking agent used to crosslink the acrylic resin compositionused to make the base layer (B3) is an isocyanate crosslinking agentthat is of room temperature curing type and easy to handle. An aliphaticisocyanate or an alicyclic isocyanate is particularly preferred.Specific examples of the isocyanate crosslinking agent include thoseenumerated above with respect to the base layer (B1) of the firstaspect.

The crosslinking agent is used in an amount of 1.1 to 1.3 equivalentweights based on the hydroxyl value of the acrylic resin compositionused to make the base layer (B3). Too large an amount of thecrosslinking agent results in reduced flexibility. Too small an amountof the crosslinking agent results in reduced heat resistance anddurability.

The base layer (B3) has a thickness of 30 to 80 μm, preferably 40 to 70μm. With the thickness of 30 μm or more, the laminate is provided withsufficient flexibility. With the thickness of 80 μm or less, the sheetis prevented from destruction during attachment.

The laminate of the third aspect of the invention further includes adestructible layer (C3) laminated with the base layer (B3). Thedestructible layer (C3) is made of a crosslinked acrylic resin obtainedby crosslinking a mixture of an acrylic resin composition and polymerbeads with an isocyanate crosslinking agent. The acrylic resincomposition has a hydroxyl value of 20 to 35 mg KOH/g, preferably 25 to30 mg KOH/g, and includes (C3-1) an acrylic polymer having a reactivefunctional group, (C3-2) a glycol compound, and (C3-3) a coloringmaterial containing an acrylic resin having a reactive hydroxyl groupand a pigment dispersed in the acrylic resin.

The acrylic polymer (C3-1) having a reactive functional group for use tomake the destructible layer (C3) may be chosen from those usable to makethe pigmented layer (A3).

Similarly to the base layer (B3), the destructible layer (C3) contains aglycol compound to control its flexibility. The glycol compound may beused in an amount of 1% to 10%, preferably 2% to 8%, more preferably 3%to 6%, by weight based on the total solids content of the destructiblelayer (C3), i.e., the solid content of the pigment and the resin of thedestructible layer. With a glycol compound content of 1 wt % or less,the film can form a crack on bending in attachment. With a glycolcompound content of 10 wt % or more, the laminate (e.g., a label)attached to a substrate may be reusably strippable without damage.

The destructible layer (C3) may be colored and may be transparent. Wherecolored, the destructible layer (C3) is colored preferably in the samehue as the base layer (B3). The same coloring material as used in thebase layer (B3), i.e. a reactive hydroxyl-containing acrylic resinhaving a pigment dispersed therein, may be used. The recommended pigmentcontent in the destructible layer (C3) is 10% to 120%, preferably 20% to100%, by weight. A pigment content less than 5 wt % is unable to assurehiding properties. Using 60 wt % or more of the pigment can result inpoor film forming properties in making the layer (C3).

The destructible layer (C3) contains polymer beads as a brittlenessimparting component. Preferred polymer beads include acrylic beads,styrene beads, and silicone beads in terms of narrow particle sizedistribution. Taking heat resistance into consideration, acrylic beadsare the most preferred.

The polymer beads must have an average particle size of not greater thanthe thickness of the destructible layer (C3). The average particle sizeof the polymer beads is 1 to 100 μm, 1 to 150 μm, preferably 1 to 80 μm,5 to 100 μm, more preferably 10 to 80 μm. Particles smaller than 1 μmare unable to impart brittleness. Particles greater than 150 μm areliable to cause cracking during attachment.

The polymer beads content is 10% to 280%, preferably 10% to 200%, morepreferably 30% to 100%, by volume based on the resin of the destructiblelayer (C3). At a polymer beads content of 10 vol % or less, no effectsof polymer beads is produced. Addition of 280% or more by volume of thepolymer beads results in void formation between the particles, which cancause cracking during attachment.

The acrylic resin composition used to make the destructible layer (C3)has a hydroxyl value of 20 to 35 mg KOH/g, preferably 25 to 30 mg KOH/g.With a hydroxyl value of at least 20 mg KOH/g, the resin compositionundergoes sufficient crosslinking to acquire heat resistance. With ahydroxyl value less than 35 mg KOH/g, workability is secured.

The crosslinking agent used to crosslink the acrylic resin compositionof the destructible layer (C3) is the same isocyanate crosslinking agentas useful in the base layer (B3). An aliphatic isocyanate or analicyclic isocyanate is particularly preferred.

The crosslinking agent is used in an amount of 1.1 to 1.3 equivalentweights based on the total hydroxyl value of the acrylic resincomposition of the destructible layer (C3). Too large an amount of thecrosslinking agent results in reduced flexibility. Too small an amountof the crosslinking agent results in reduced heat resistance anddurability.

The destructible layer (C3) has a thickness of 20 to 100 μm, preferably40 to 80 μm. With a thickness of at least 20 μm, the destructible layer(C3) is able to exert sufficient breaking stress on the laminate. With athickness of 100 μm or less, sufficient attachment workability issecured.

The laminate of the third aspect has a tensile strength of at least 20N/10 mm, preferably 25 N/10 mm or more, measured in accordance with JISK7127. A label formed of the laminate with a tensile strength of lessthan 20 N/10 mm has poor workability in attachment due to lack ofstiffness.

Similarly to the label having the laminate of the first aspect, when alabel having the laminate of the third aspect is attached to a substrateand peeled off by the hand or with a tool, the film is destroyed.Destruction occurs through various mechanisms. In frequent cases, thelaminate unrecoverably undergoes cracking due to the strain caused bythe stress accompanying peeling. Known brittle laminates designed towithstand use in high temperatures and be destroyed when peeled are sohard and brittle that they have poor workability or poor conformabilityto the contour of a substrate when attached to a substrate as a label.In contrast, the laminate of the invention exhibits both workability anddestructibility as well as heat resistance by virtue of the elaboratedcombinations of a resin component having a reaction functional group anda crosslinking agent.

Similarly to the laminate of the first aspect, the laminate of the thirdaspect may further include an adhesive layer with which it is attachedto a substrate. The adhesive layer has a thickness of 15 to 100 μm,preferably 20 to 70 μm, more preferably 25 to 45 μm. A thickness of 15μm or more assures sufficient adhesion to a substrate. A thickness ofless than 100 μm is suitable for the attachment and economicallyadvantageous.

Similarly to the first aspect, the adhesive layer preferably has anadhesive strength of at least 5 N/25.4 mm as measured in a 180 degreepeel test, in which a 25.4 mm wide strip of the laminate is left tostand for 24 hours as attached to a substrate and then peeled at 180°using a tensile tester. With the adhesive strength less than 5 N/25.4mm, the laminate attached to a curved surface tends to have itsperipheral portion lifted.

Similarly to the first aspect, the adhesive layer may be made of anyresins. However, an acrylic adhesive is preferred in view ofweatherability, transparency, and anti-yellowing properties. If desired,the acrylic adhesive may contain additives, such as a tackifier, a UVabsorber, a photo stabilizer, and an antioxidant.

The laminate of the third aspect is prepared by coating, or printing(e.g., gravure printing) a pigmented layer-forming resin having apigment dispersed therein to a carrier film, drying the resin applied toform a pigmented layer (A3), coating, or printing (e.g., gravureprinting) a base layer-forming resin having a pigment dispersed thereinto the pigmented layer (A3), drying the resin applied to form a baselayer (B3), coating, or printing (e.g., gravure printing) a destructiblelayer-forming resin to the base layer (B3), and drying the resin appliedto form a destructible layer (C3). The laminate may be otherwiseprepared using known methods for producing a laminate film, for examplea method including forming pigmented dry films corresponding to thelayers and laminating the dry films by thermopress bonding or with anadhesive or a combination of these methods.

As illustrated in FIG. 3, the laminate of the third aspect includes anadhesive layer 4, (C3) a destructible layer 3 that is destroyed onpeeling the laminate, (B3) a base layer 2, and (A3) a pigmented layer 1that is removability by irradiation with laser light, being stacked oneon top of another in the order named. On imagewise irradiating thelaminate with laser light, the (A3) pigmented layer 1 is removed in thepattern of laser irradiation to expose the (B3) base layer 2. As aresult, a desired image appears on the laminate as a color contrastbetween the (A3) pigmented layer 1 and the (B3) base layer 2. The (C3)destructible layer 3 contains beads 5 as a brittleness impartingcomponent.

Lasers used for irradiation include those described above with respectto the first aspect. CO₂ lasers, Nd:YAG lasers, and so on that areinexpensive and relatively easy to operate are generally used.

The laminate according to any aspect of the invention is markable usinga laser printer to provide a desired image according to purpose. It iseffectively used as a label or a sheet for a lone period of time in ahigh temperature environment as marked with, for example, a serialnumber or a date to provide identifying information, such as productiondate and use-by date, for the purpose of product management and qualityguarantee. After once attached to a substrate, the laminate is destroyedon being peeled off the substrate. That is, the laminate provides atamper-proof label prevented from unauthorized reuse. In particular, thelaminate of the third aspect is effectively useful even in anenvironment in which it is subjected to 150° C. or higher temperaturesfor a long period of time.

EXAMPLES

The invention will now be illustrated in greater detail with referenceto Examples and Comparative Examples, but it should be understood thatthe invention is not construed as being limited thereto. Unlessotherwise noted, all the parts are by weight.

Examples of First Aspect of the Invention Reference Example 1

Fifty parts by weight of an acrylic resin KP-1876 (from Nikka Polymer),50 parts by weight of an acrylic resin 210005 (from Nippon Carbide), 5parts by weight of CAB (20% solution in MIBK), 18 parts by weight of amelamine crosslinking agent MS-11 (from Sanwa Chemical), 4.5 parts byweight of a curing catalyst CT-5 (from Sanwa Chemical), 15 parts byweight of a coloring material UTCO-591B (from Dainichiseika Color &Chemicals), 15 parts by weight of MIBK, and 30 parts by weight oftoluene were mixed to prepare a black resin solution for pigmentedlayer.

Reference Example 2

Fifty parts by weight of an acrylic resin 2100U5 (from Nippon Carbide),100 parts by weight of a coloring material UTCO-501 White (fromDainichiseika Color & Chemicals), 7 parts by weight (corresponding to1.1 equivalent weights based on the reactive functional group of theresin) of an isocyanate crosslinking agent Coronate HK (from NipponPolyurethane Industry), 10 parts by weight of a glycol compoundPTMG-1000M (from Sanyo Chemical Industries), and 10 parts by weight ofSolvesso 100 (from Exxon Mobile) were mixed to prepare a white resinsolution for base layer.

Reference Example 3

A fifty parts by weight of an acrylic resin SZ6226 (from NipponCarbide), A hundred parts by weight of a coloring material UTCO-501White from (Dainichiseika Color & Chemicals), 7 parts by weight(corresponding to 1.0 equivalent weight based on the reactive functionalgroup of the resin) of an isocyanate crosslinking agent Coronate HK(from Nippon Polyurethane Industry), and 25 parts by weight of Solvesso100 (from Exxon Mobile) were mixed to prepare a white resin solution fordestructible layer.

Reference Example 4

A hundred parts by weight of an acrylic adhesive PE-121 (from NipponCarbide) and 1.8 parts by weight of a crosslinking agent CK-401 (fromNippon Carbide) were mixed to prepare a pressure sensitive adhesivesolution A.

Example 1

The black resin solution for pigmented layer prepared in ReferenceExample 1 was applied to a PET film S75 (from Teijin Du Pont Films) anddried at 90° C. for 2 minutes and then at 140° C. for 3 minutes to forma pigmented layer with a thickness of 15 μm.

The white resin solution for base layer prepared in Reference Example 2was applied to the pigmented layer to a dry thickness of 50 μm and driedunder the same condition as for the pigmented layer to prepare alaminate film having the pigmented layer and a base layer.

The white resin solution for destructible layer prepared in ReferenceExample 3 was applied to the base layer to a dry thickness of 50 μm tomake a laminate film having the pigmented layer, the base layer, and adestructible layer.

The pressure sensitive adhesive solution A obtained in Reference Example4 was applied to a PET film MRG50 (from Mitsubishi Chemical PolyesterFilm) and dried at 100° C. for 2 minutes to form an adhesive layer witha thickness of 30 μm. The laminate film and the adhesive layer/PET filmcomposite were joined to bring the destructible layer and the adhesivelayer into contact with each other, and the two PET films were strippedoff to make a laser-markable brittle laminate.

The composition of the resulting laminate, the results of tensile tests,and the results of performance evaluation are shown in Tables 1 and 2below.

Example 2

A laminate film having a pigmented layer and a base layer was preparedin the same manner as in Example 1, except for changing the amount ofeach of the Coronate and PTMG-1000M in the white resin solution for baselayer to 5 parts by weight. The amount of the Coronate was 0.8equivalent weights based on the reactive functional group of the resin.

A destructible layer was formed on the base layer using a white resinsolution for destructible layer having the same composition as inExample 1, except for containing an acrylic resin SZ6227 (from NipponCarbide) in place of SZ6226, changing the amount of the isocyanatecrosslinking agent Coronate HK to 10 parts by weight (1.4 equivalentweights based on the reactive functional group of the resin), andfurther containing 5 parts by weight of PTMG-1000M.

On the resulting laminate having the pigmented layer, the base layer,and the destructible layer was formed a pressure sensitive adhesivelayer in the same manner as in Example 1 to make a laser-markablebrittle laminate.

The composition of the resulting laminate, the results of tensile tests,and the results performance evaluation are shown in Tables 1 and 2.

Example 3

A laminate film having a pigmented layer and a base layer was preparedin the same manner as in Example 1, except for using 7 parts by weightof the isocyanate crosslinking agent Coronate HK (1.1 equivalent weightsbased on the reactive functional group of the resin) and 5 parts byweight of PTMG-1000M in the white resin solution for base layer.

A destructible layer was formed on the base layer using a white resinsolution for destructible layer having the same composition as inExample 1, except for further containing 5 parts by weight ofPTMG-1000M.

On the resulting laminate having the pigmented layer, the base layer,and the destructible layer was formed a pressure sensitive adhesivelayer in the same manner as in Example 1 to make a laser-markablebrittle laminate.

The composition of the resulting laminate, the results of tensile tests,and the results performance evaluation are shown in Tables 1 and 2.

Example 4

A laser-markable brittle laminate was made in the same manner as inExample 3, except for changing the dry thicknesses of the base layer andthe destructible layer to 60 μm and 40 μm, respectively.

The composition of the resulting laminate, the results of tensile tests,and the results performance evaluation are shown in Tables 1 and 2.

Example 5

A laser-markable brittle laminate was made in the same manner as inExample 3, except for changing the dry thicknesses of the base layer andthe destructible layer to 30 μm and 70 μm, respectively.

The composition of the resulting laminate, the results of tensile tests,and the results performance evaluation are shown in Tables 1 and 2.

Example 6

A laminate film having a pigmented layer and a base layer was preparedin the same manner as in Example 1, except for changing the amount ofPTMG-1000M in the white resin solution for base layer to 5 parts byweight.

A destructible layer was formed on the base layer using a white resinsolution for destructible layer having the same composition as inExample 1, except for using an acrylic resin 210005 in place of SZ6226and further containing 5 parts by weight of PTMG-1000M and 16 parts byweight of polymer beads Art Pearl GR-300 (from Negami Chemicalindustrial Co., Ltd.). The amount of Coronate HK was 1.1 equivalentweights based on the functional group of the resin. On the resultinglaminate having the pigmented layer, the base layer, and thedestructible layer was formed a pressure sensitive adhesive layer in thesame manner as in Example 1 to make a laser-markable brittle laminate.

The composition of the resulting laminate, the results of tensile tests,and the results performance evaluation are shown in Tables 1 and 2.

Example 7

A laminate film having a pigmented layer and a base layer was preparedin the same manner as in Example 1, except for changing the amount ofPTMG-1000M in the white resin solution for base layer to 5 parts byweight.

A destructible layer was formed on the base layer using a white resinsolution for destructible layer having the same composition as inExample 1, except for further containing 5 parts by weight of PTMG-1000Mand 30 parts by weight of polymer beads Art Pearl GR-300 (from NegamiChemical industrial). On the resulting laminate having the pigmentedlayer, the base layer, and the destructible layer was formed a pressuresensitive adhesive layer in the same manner as in Example 1 to make alaser-markable brittle laminate.

Comparative Example 1

A laser-markable brittle laminate was made in the same manner as inExample 1, except for omitting the destructible layer and changing thethickness of the base layer to 100 μm.

The composition of the resulting laminate, the results of tensile tests,and the results performance evaluation are shown in Tables 1 and 2.

Comparative Example 2

A laser-markable brittle laminate was made in the same manner as inExample 1, except for omitting the base layer and changing the thicknessof the destructible layer to 100 μm.

The composition of the resulting laminate, the results of tensile tests,and the results performance evaluation are shown in Tables 1 and 2.

Comparative Example 3

A laminate film having a pigmented layer, a base layer, and adestructible layer was made in the same manner as in Example 1 with thefollowing exceptions. The acrylic resin 2100U5 and CAB were omitted fromthe black resin solution for pigmented layer. The amounts of themelamine crosslinking agent MS-11 and the curing catalyst CT-5 in theblack resin solution for pigmented layer were changed to 9 parts byweight and 2 parts by weight, respectively. The amount of PTMG-1000M inthe white resin solution for base layer was changed to 10 parts byweight. The white resin solution for destructible layer furthercontained 5 parts by weight of PTMG-1000M.

In the same manner as in Example 1, a pressure sensitive adhesive layerwas formed on the laminate film to make a laser-markable brittlelaminate.

The composition of the resulting laminate, the results of tensile tests,and the results performance evaluation are shown in Tables 1 and 2.

Comparative Example 4

A laminate film having a pigmented layer and a base layer was preparedin the same manner as in Example 1, except for changing the amount ofthe isocyanate crosslinking agent Coronate HK in the white resinsolution for base, layer to 10 parts by weight (1.6 equivalent weightsbased on the reactive functional group of the resin) and omittingPTMG-1000M from the same solution.

A destructible layer was formed on the base layer using a white resinsolution for destructible layer having the same composition as inExample 1, except for changing the amount of the isocyanate crosslinkingagent Coronate HK to 10 parts by weight (1.4 equivalent weights based onthe reactive group of the resin) and omitting PTMG-1000M.

In the same manner as in Example 1, a pressure sensitive adhesive layerwas formed on the laminate film to make a laser-markable brittlelaminate. The composition of the resulting laminate, the results oftensile tests, and the results performance evaluation are shown inTables 1 and 2.

Comparative Example 5

A laminate having a pigmented layer, a base layer, and a destructiblelayer was made in the same manner as in Example 6, except for changingthe dry thicknesses of the pigmented layer, the base layer, and thedestructible layer to 40 μm, 40 μm, and 35 μm, respectively.

In the same manner as in Example 1, a pressure sensitive adhesive layerwas formed on the laminate to make a laser-markable brittle laminate.

The composition of the resulting laminate, the results of tensile tests,and the results performance evaluation are shown in Tables 1 and 2.

The physical properties of the laser-markable brittle laminates obtainedin Examples 1 to 7 and Comparative Examples 1 to 5 were measured andevaluated in accordance with the following methods (1) through (8).

(1) Tensile Elongation at Break (JIS K7127)

Tensile tester: Tensilon TM-100 (from Toyo Baldwin)

Specimen width: 10 mm

Initial separation between jaws: 100 mm

Testing speed: 200 mm/min

The measurement was taken five times per sample to obtain an average.

(2) Tensile Breaking Strength (JIS K7127)

The same as in (1) above.

(3) Non-Reusability

A 1.5 cm wide, 5 cm long piece of the laminate was attached to a whitecoated plate and allowed to stand at 23° C. for 72 hours and thenremoved from the coated plate using a cutter knife. The removed laminatewas checked if it was reusable or non-reusable as a result of, forexample, destruction. The test was repeated ten times per sample. Thenon-reusability of the laminate was rated as follows.

Good: The sample became non-reusable nine or more times out of ten.

Medium: The sample became non-reusable seven or eight times out of ten.

Poor: The sample became non-reusable six or fewer times out of ten.

(4) Attachment Workability

A 1.5 cm wide, 5 cm long label having the laminate, the pressuresensitive adhesive layer, and a release liner was prepared. The releaseliner was stripped, and the label was attached to a white coated paper.During the attachment operation, the label was checked if a break(crack) formed. A total of 50 labels were tested per sample. Theattachment workability of the laminate was evaluated from the number ofthe labels that broke during the attachment operation and rated asfollows.

Good: No or only one label out of 50 broke.

Medium: Two to five labels out of 50 broke.

Poor: Six or more labels out of 50 broke.

(5) Resistance to Laser Strike-Through

The laminate was marked with the capital letter “A” with a line width of130 μm, 250 μm, and 400 μm by laser ablation using a laser marker LP-430(from Sun Limited) at an output of 10 W and a scan speed of 500 mm/s.The release liner was removed, and the letters were observed withtransmitted light from the adhesive layer side. A laminate having theirradiated part partially remaining was rated “good”, and a laminatehaving the irradiated part completely ablated was rated “poor”.

(6) Sharpness of Laser Marking

The sample marked with the letter A as obtained in (5) above wasevaluated for the sharpness of the mark by observing the edge of themark, i.e., the ablated portion under an optical microscope BX51 (fromOlympus).

Good: The edge of the mark was sharp and neat.

Medium: Part of the edge of the mark had burr.

Poor: The entire edge of the mark had burr.

(7) Legibility of Bar Code

The laminate was marked with an EAN128 bar code under the same conditionas in (5) above. The bar code thus marked was read with a bar codereader ten times. The mark that was readable ten times was rated “good”,while the mark that was unreadable one or more times was rated “poor”.

(8) Heat Resistance

The laminate was marked with an EAN128 bar code in the same manner as in(7) above and allowed to stand at 150° C. for 1000 hours. Thereafter,the bar code was read with a bar code reader ten times. The mark thatwas readable ten times was rated “good”, while the mark that wasunreadable one or more times was rated “poor”.

TABLE 1 Example No. Comparative Example No. 1 2 3 4 5 6 7 1 2 3 4 5Pigmented Composition KP-1876 50 50 50 50 50 50 50 50 50 100 — 50 Layer2100U5 50 50 50 50 50 50 50 50 50 — 100 50 CAB 5 5 5 5 5 5 5 5 5 — 10 5MS-11 18 18 18 18 18 18 18 18 18 9 18 18 CT-5 4.5 4.5 4.5 4.5 4.5 4.54.5 4.5 4.5 2 4.5 4.5 MBK 15 15 15 15 15 15 15 15 15 15 15 15 Toluene 3030 30 30 30 30 30 30 30 30 30 30 UTCO-591 Black 15 15 15 15 15 15 15 1515 15 15 15 Thickness (μm) 15 15 15 15 15 15 15 15 15 15 15 40 TensileElongation at Break (%) 3 3 3 3 3 3 3 3 3 22 1 3 Base Composition 2100U550 50 50 50 50 50 50 50 — 50 50 50 Layer UTCO-501 White 100 100 100 100100 100 100 100 — 100 100 100 Coronate HK 7 5 7 7 7 7 7 7 — 7 10 7Solvesso 100 10 10 10 10 10 10 10 10 — 10 10 10 PTMG-1000M 10 5 5 5 5 55 5 — 10 — 5 Thickness (μm) 50 50 50 60 30 50 50 100 — 50 50 35 TensileElongation at Break (%) 43 28 21 23 17 24 18 38 — 90 6 20 DestructibleComposition 2100U5 — — — — — 50 — — — — — 50 Layer SZ6226 50 — 50 50 50— 50 — — 50 — — SZ6227 — 50 — — — — — — 50 — 50 — UTCO-501 white 100 100100 100 100 100 100 — 100 100 100 100 Coronate HK 7 10 7 7 7 7 7 — 7 710 7 Solvesso 100 25 25 25 25 25 25 25 — 25 25 25 25 PTMG-1000M — 5 5 55 5 5 — 5 5 — 5 Art Pearl GR-300 — — — — — 16 30 — — — — 16 Thickness(μm) 50 50 50 40 70 50 50 — 100 50 50 40 Tensile Elongation at Break (%)5 3 8 8 9 8 8 — 3 8 1 8 Tensile Strength of Laminate (N/10 mm) 30 32 2826 38 42 48 16 44 14 63 49 Tensile Elongation at Break of Laminate (%) 86 16 24 14 8 6 35 3 62 1 8 Adhesive Compo- PE-121 100 100 100 100 100100 100 100 100 100 100 100 Layer sition CK-401 1.8 1.8 1.8 1.8 1.8 1.81.8 1.8 1.8 1.8 1.8 1.8 Thickness (μm) 30 30 30 30 30 30 30 30 30 30 3030

TABLE 2 Laser Marking Test Non-reusability Attachment Resistance toLaser Heat (Peeling/Reattachment) Workability Strike-Through SharpnessLegibility Resistance Example 1 good good good good good good Example 2good medium good good good good Example 3 good good good good good goodExample 4 medium good good good good good Example 5 medium good goodgood good good Example 6 good good good good good good Example 7 goodgood good good good good Comp. Example 1 poor good good good good poorComp. Example 2 good poor good good good poor Comp. Example 3 poor goodgood good good good Comp. Example 4 poor poor good good good good Comp.Example 5 poor medium poor poor poor good

Examples of Second Aspect of Invention Reference Example 5

Fifty parts by weight of an acrylic resin KP-1876 (from Nikka Polymer),20 parts by weight of CAB (20% solution in MIBK), 100 parts by weight ofa coloring material UTCO-501 White (from Dainichiseika Color &Chemicals), 9 parts by weight of a melamine crosslinking agent MS-11(from Sanwa Chemical) (1.0 equivalent weight based on the reactivefunctional group of the resin), 3 parts by weight of a curing catalystCT-5 (from Sanwa Chemical), 2 parts by weight of a glycol compound toPTMG-1000M (from Sanyo Chemical Industries), and 5 parts by weight ofSolvesso 100 (from Exxon Mobile) were mixed to prepare a white resinsolution for destructible layer.

Reference Example 6

Fifty parts by weight of an acrylic resin 2100U5 (from Nippon Carbide),100 parts by weight of a coloring material UTCO-501 White (fromDainichiseika Color & Chemicals), 20 parts by weight (corresponding to1.0 equivalent weight based on the reactive functional group of theresin) of an isocyanate crosslinking agent Sumidule N75 (from SumitomoChemical), 6 parts by weight of a glycol compound PTMG-1000M (from SanyoChemical Industries), and 5 parts by weight of Solvesso 100 (from ExxonMobile) were mixed to prepare a white resin solution for base layer.

Example 8

The black resin solution for pigmented layer prepared in ReferenceExample 1 was applied to a PET film S75 (from Teijin Du Pont Films) anddried at 90° C. for 2 minutes and then at 140° C. for 3 minutes to forma pigmented layer with a thickness of 15 μm.

The white resin solution for destructible layer prepared in ReferenceExample 5 was applied to the pigmented layer to a dry thickness of 30 μmand dried under the same condition as for the pigmented layer to preparea laminate film having the pigmented layer and a destructible layer.

The white resin solution for base layer prepared in Reference Example 6was applied to the destructible layer to a dry thickness of 70 μm tomake a laminate having the pigmented layer, the destructible layer, anda base layer.

Separately, the pressure sensitive adhesive solution A obtained inReference Example 4 was applied to a PET film MRG50 (from MitsubishiChemical Polyester Film) and dried at 100° C. for 2 minutes to form anadhesive layer with a thickness of 30 μm. The laminate film and theadhesive layer/PET film composite were joined to bring the base layerand the adhesive layer into contact with each other. The two PET filmswere stripped off to make a laser-markable laminate.

The composition of the resulting laminate, the results of tensile tests,and the results performance evaluation are shown in Tables 3 and 4below.

Example 9

A laser-markable brittle laminate was made in the same manner as inExample 8, except for changing the dry thicknesses of the destructiblelayer and the base layer to 60 μm and 40 μm, respectively.

The composition of the resulting laminate, the results of tensile tests,and the results performance evaluation are shown in Tables 3 and 4.

Examples 10 and 11

Laminates having a pigmented layer, a destructible layer, and a baselayer were obtained in the same manner as in Examples 8 and 9, exceptfor using 50 parts by weight of an acrylic resin SZ6226 (from NipponCarbide) as a resin of the base layer (the amount of Sumidulecorresponded to 0.9 equivalent weights based on the reactive functionalgroup of the resin). The composition of the resulting laminates, theresults of tensile tests, and the results performance evaluation areshown in Tables 3 and 4.

Example 12

A laminate film having a pigmented layer and a destructible layer wasprepared in the same manner as in Example 8, except for using 50 partsby weight of an acrylic resin 2100U5 (from Nippon Carbide) and replacingMS-II as a crosslinking agent and CT-5 with 7 parts by weight(corresponding to 1.1 equivalent weights based on the reactivefunctional group of the resin) of an isocyanate crosslinking agentCoronate HK (from Nippon Polyurethane Industry). A base layer was thenformed using the same white resin solution as used in Example 8, exceptfor using an acrylic resin SZ6227 (from Nippon Carbide) (the amount ofSumidule corresponded to 0.9 equivalent weights based on the reactivefunctional group of the resin) and changing the amount of PTMG-1000M to4 parts by weight, to prepare a laminate having the pigmented layer, thedestructible layer, and a base layer. A pressure sensitive adhesivelayer was formed in the same manner as in Example 8 to make alaser-markable brittle laminate.

The composition of the resulting laminate, the results of tensile tests,and the results performance evaluation are shown in Tables 3 and 4.

Example 13

A laminate was made in the same manner as in Example 12, except forchanging the dry thicknesses of the destructible layer and the baselayer to 60 μm and 40 μm, respectively.

The composition of the resulting laminate, the results of tensile tests,and the results performance evaluation are shown in Tables 3 and 4.

Comparative Example 6

A laser-markable brittle laminate was made in the same manner as inExample 8, except for omitting the base layer and changing thethicknesses of the pigmented layer and the destructible layer to 20 μmand 80 μm, respectively.

The composition of the resulting laminate, the results of tensile tests,and the results performance evaluation are shown in Tables 3 and 4.

Comparative Example 7

A laser-markable brittle laminate was made in the same manner as inExample 8, except for omitting the destructible layer and changing thethicknesses of the pigmented layer and the base layer to 20 μm and 80μm, respectively.

The composition of the resulting laminate, the results of tensile tests,and the results performance evaluation are shown in Tables 3 and 4.

Comparative Examples 8 to 10

Laminates were obtained in the same manner as in Example 8, except forchanging the compositions and thicknesses of the pigmented layer, thedestructible layer, and the base layer as shown in Table 3. A pressuresensitive adhesive layer was provided on each laminate in the samemanner as in Example 8 to make laser-markable brittle laminates.

The composition of the resulting laminates, the results of tensiletests, and the results performance evaluation are shown in Tables 3 and4.

The physical properties of the brittle, laser-markable laminatesobtained in Examples 8 to 13 and Comparative Examples 6 to 10 weremeasured or evaluated by the methods (1) to (8) described above.

TABLE 3 Example No. Comparative Example No. 8 9 10 11 12 13 6 7 8 9 10Pigmented Composition KP-1876 50 50 50 50 50 50 50 50 100 — 50 Layer2100U5 50 50 50 50 50 50 50 50 — 100 50 CAB 5 5 5 5 5 5 5 5 — 10 5 MS-1118 18 18 18 18 18 18 18 9 18 18 CT-5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 24.5 4.5 MBK 15 15 15 15 15 15 15 15 15 15 15 Toluene 30 30 30 30 30 3030 30 30 30 30 UTCO-591 Black 15 15 15 15 15 15 15 15 15 15 15 Thickness(μm) 15 15 15 15 15 15 20 20 15 15 40 Tensile Elongation at Break (%) 33 3 3 3 3 3 3 22 1 3 Destructible Composition KP-1876 50 50 50 50 — — —— — — 50 Layer CAB 20 20 20 20 — — — — — — 20 MS-11 9 9 9 9 — — — — — —9 CT-5 3 3 3 3 — — — — — — 3 2100U5 — — — — 50 50 50 — 50 50 — UTCO-501White 100 100 100 100 100 100 100 — 100 100 100 Coronate HK — — — — 7 77 — 7 7 — Solvesso 100 5 5 5 5 5 5 5 — 5 5 5 PTMG-1000M 2 2 2 2 2 2 1 —5 — 2 Art Pearl GR-300 — — — — — — — — — — — Thickness (μm) 30 60 30 6030 60 80 60 60 35 Tensile Elongation at Break (%) 6 7 6 7 5 6 6 — 25 1 6Base Composition 2100U5 50 50 — — — — — 50 50 50 50 Layer SZ6226 — — 5050 — — — — — — — SZ6227 — — — — 50 50 — — — — — UTCO-501 White 100 100100 100 100 100 — 100 100 100 100 Coronate HK — — — — — — — — 7 7 —Sumidule N75 20 20 20 20 20 20 — 20 — — 20 Solvesso 100 5 5 5 5 5 5 — 55 5 5 PTMG-1000M 6 6 6 6 4 4 — 6 10 — 6 Art Pearl GR-300 — — — — — — — —— — — Thickness (μm) 70 40 70 40 70 40 — 80 40 40 40 Tensile Elongationat Break (%) 16 13 18 15 17 14 — 18 80 1 14 Tensile Strength of Laminate(N/10 mm) 38 42 40 52 42 58 45 19 15 63 50 Tensile Elongation at Breakof Laminate (%) 8 6 10 13 17 12 4 16 6 1 7 Adhesive Compo- PE-121 100100 100 100 100 100 100 100 100 100 100 Layer sition CK-401 1.8 1.8 1.81.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 Thickness (μm) 30 30 30 30 30 30 30 3030 30 30

TABLE 4 Laser Marking Test Non-reusability Attachment Resistance toLaser Heat (Peeling/Reattachment) Workability Strike-Through SharpnessLegibility Resistance Example 8 good good good good good good Example 9medium good good good good good Example 10 good good good good good goodExample 11 medium good good good good good Example 12 good good goodgood good good Example 13 good good good good good good Comp. Example 6good poor good good good poor Comp. Example 7 poor good good good goodpoor Comp. Example 8 poor poor good medium good good Comp. Example 9good medium good good medium good Comp. Example 10 good poor poor poorpoor good

Examples of Third Aspect of the Invention Reference Example 7 Resin ofPigmented Layer

Fifty parts by weight of an acrylic resin KP-1876 (from Nikka Polymer),50 parts by weight of an acrylic resin 2100U7 (from Nippon Carbide), 5parts by weight of CAB (20% solution in MIBK), 15 parts by weight of acoloring material FPGS-5910 (black pigment from Dainichiseika Color &Chemicals), and 23 parts by weight of MIBK were mixed. To the mixturewere added 18 parts by weight of a melamine crosslinking agent MS-11(from Sanwa Chemical) and 4.5 parts by weight of a curing catalyst CT-5(from Sanwa Chemical) to prepare a black resin solution for pigmentedlayer.

Reference Example 8 Preparation of Coloring Materials

Twenty-one parts by weight of an acrylic resin MN-0500 (from NipponCarbide; hydroxyl value: 10 mg KOH/g). 58 parts by weight of titaniumoxide CR-90 (from Ishihara Sangyo), 3 parts by weight of a glycolcompound PTMG-1000M (from Sanyo Chemical Industries; hydroxyl value: 111mg KOH/g), and 21 parts by weight of ethyl acetate were mixed in adisper stirrer to prepare coloring material A (hydroxyl value: 5.3 mgKOH/g).

Coloring materials B to E were prepared in the same manner as forcoloring material A, except for changing the composition as shown inTable 5 below.

TABLE 5 Hydroxyl Value (mg Coloring Material KOH/g) A B C D EComposition: MN-500 10 21 — — — — MN-501 32 — 21 — — — MN-502 61 — — 21— — MN-503 3 — — — 21 — MN-504 85 — — — — 21 CR-90 — 58 58 58 58 58Ethyl Acetate — 21 21 21 21 21 PTMG-1000M 111 3 3 3 3 3 Hydroxyl Valueof Coloring Material 5.3 9.8 15.7 3.8 20.6 (mg KOH/g)

Reference Example 9 Resin of Base Layer

Twenty parts by weight of an acrylic resin 2100U7 (from Nippon Carbide:hydroxyl value: 77.2 mg KOH/g), 100 parts by weight of coloring materialA (hydroxyl value: 5.3 ma KOH/g), 3 parts by weight of a glycol compoundPTMG-1000M (From Sanyo Chemical Industries; hydroxyl value: 111 mgKOH/g), and 10 parts by weight of Solvesso 100 (from Exxon Mobile) weremixed to prepare a resin composition having a hydroxyl value of 18.3 mgKOH/g. To the composition was added 10.8 parts by weight (1.2 equivalentweights based on the hydroxyl value) of an isocyanate crosslinking agentCoronate HK (from Nippon Polyurethane Industry) to prepare a white resinsolution for base layer.

Other resins for base layer were prepared in the same manner asdescribed above, except for changing the composition as shown in Table 6below.

Reference Example 10 Resin for Destructible Layer

Fifty parts by weight of an acrylic resin 210007 (from Nippon Carbide;hydroxyl value: 77.2 me KOH/g), 100 parts by weight of coloring materialA (hydroxyl value: 5.3 mg KOH/g), 5 parts by weight of a glycol compoundPTMG-1000M (From Sanyo Chemical Industries: hydroxyl value: 111 mgKOH/g), and 25 parts by weight of Solvesso 100 (from Exxon Mobile) weremixed. Sixteen parts by weight of polymer beads Art Pearl GR-300 (fromNegami Chemical industrial Co. Ltd.) were added thereto to prepare aresin composition having a hydroxyl value of 25.2 mg KOH/g. To thecomposition was added 22.2 parts by weight (1.2 equivalent weights basedon the hydroxyl value) of an isocyanate crosslinking agent Coronate HK(from Nippon Polyurethane Industry) to prepare a white resin solutionfor destructible layer.

Example 14

The black resin solution for pigmented layer prepared in ReferenceExample 7 was applied to a PET film S75 (from Teijin Du Pont Films) anddried at 90° C. for 2 minutes and then at 140° C. for 3 minutes to forma pigmented layer with a thickness of 15 μm.

The white resin solution for base layer prepared in Reference Example 9was applied to the pigmented layer to a dry thickness of 50 μm and driedunder the same condition as for the pigmented layer to prepare alaminate film having the pigmented layer and a base layer.

The white resin solution for destructible layer prepared in ReferenceExample 10 was applied to the base layer to a dry thickness of 55 μm tomake a laminate having the pigmented layer, the base layer, and adestructible layer.

Separately, the pressure sensitive adhesive solution A obtained inReference Example 4 was applied to a PET film MRG50 (from MitsubishiChemical Polyester Film) and dried at 100° C. for 2 minutes to form anadhesive layer with a thickness of 30 μm. The two PET films were joinedto bring the base layer and the adhesive layer into contact with eachother and then stripped off to provide a laser-markable brittlelaminate.

The composition of the resulting laminate and the results of testing areshown in Tables 6 and 7 below.

Examples 15 to 25

Laser-markable brittle laminates were made in the same manner as inExample 14, except for changing the resin compositions as shown in Table6. The composition of the resulting laminates and the results of testingare shown in Tables 6 and 7.

Comparative Example 11

A laser-markable brittle laminate was made in the same manner as inExample 14, except for using coloring material D in place of coloringmaterial A. The composition of the resulting laminates and the resultsof testing are shown in Tables 6 and 7.

Comparative Examples 12 to 15

Laser-markable brittle laminates were made in the same manner as inExample 14, except for changing the resin compositions as shown in Table6. The composition of the resulting laminates and the results of testingare shown in Tables 6 and 7.

TABLE 6 Example No. 14 15 16 17 18 19 20 21 22 Pigmented Acrylic Compo-KP-1876 50 50 50 50 50 50 50 50 50 Layer Resin sition 2100U7 50 50 50 5050 50 50 50 50 CAB 5 5 5 5 5 5 5 5 5 CT-5 4.5 4.5 4.5 4.5 4.5 4.5 4.54.5 4.5 FPGS-5910 15 15 15 15 15 15 15 15 15 Hydroxyl Value 63 63 63 6363 63 63 63 63 (mg KOH/g) Crosslinking MS-11 18 18 18 18 18 18 18 18 18Agent (A-4) (parts by weight) Eq. Wt. of Crosslinking Agent 1.1 1.1 1.11.1 1.1 1.1 1.1 1.1 1.1 based on OH Group Thickness (μm) 15 15 15 15 1515 15 15 15 Base Acrylic Compo- 2100U7 20 20 20 50 50 50 50 50 50 LayerResin sition Coloring Material A 100 — — 100 100 — 100 100 100 (OH Value= 5.3) Coloring Material B — 100 — — — 100 — — — (OH Value = 9.8)Coloring Material C — — 100 — — — — — — (OH Value = 15.7) ColoringMaterial D — — — — — — — — — (OH Value = 3.8) Coloring Material E — — —— — — — — — (OH Value = 20.6) PTMG-1000M 3 3 3 5 5 5 5 5 5 OH Value ofResin (mg KOH/g) 18.1 21.5 26.0 30.0 30.0 32.7 30.0 30.0 30.0Crosslinking Coronate UK 10.8 12.8 18.2 22.2 22.2 24.2 20.4 22.2 22.2Agent (B-4) (part) Eq. Wt. of Crosslinking Agent 1.2 1.2 1.2 1.2 1.2 1.21.1 1.2 1.2 based on OH Group Thickness (μm) 50 50 50 50 50 50 50 50 50Destructible Acrylic Compo- 2100U7 50 50 50 50 50 50 50 50 50 LayerResin sition Coloring Material A 100 100 100 100 — 100 100 100 100 (OHValue = 5.3) Coloring Material C — — — — — — — — — (OH Value = 15.7)Coloring Material D — — — — 100 — — — — (OH Value = 3.8) ColoringMaterial E — — — — — — — — — (OH Value = 20.6) PTMG-1000M 5 5 5 5 5 5 55 5 OH Value of Resin (mg KOH/g) 25.2 25.2 25.2 25.2 24.5 25.2 25.2 25.225.2 Art Pearl GR-300 16 16 16 16 16 16 16 16 16 Crosslinking CoronateHK 22.2 22.2 22.2 22.2 21.5 22.2 22.2 20.4 24.1 Agent (C-4) (part byweight) Eq. Wt. of Crosslinking Agent 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.11.3 based on OH Group Thickness (μm) 55 55 55 40 70 55 55 55 55 AdhesiveCompo- PE-121 100 100 100 100 100 100 100 100 100 Layer sition CK-4011.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 Thickness (Mm) 30 30 30 30 30 30 3030 30 Example No. Comparative Example No. 23 24 25 11 12 13 14 15Pigmented Acrylic Compo- KP-1876 50 50 50 50 50 50 50 50 Layer Resinsition 2100U7 50 50 50 50 50 50 50 50 CAB 5 5 5 5 5 5 5 5 CT-5 4.5 4.54.5 4.5 4.5 4.5 4.5 4.5 FPGS-5910 15 15 15 15 15 15 15 15 Hydroxyl Value63 63 63 63 63 63 63 63 (mg KOH/g) Crosslinking MS-11 18 18 18 18 18 1818 18 Agent (A-4) (parts by weight) Eq. Wt. of Crosslinking Agent 1.11.1 1.1 1.1 1.1 1.1 1.1 1.1 based on OH Group Thickness (μm) 15 15 15 1515 15 15 15 Base Acrylic Compo- 2100U7 50 50 50 20 50 60 50 50 LayerResin sition Coloring Material A 100 — — — — — 100 100 (OH Value = 5.3)Coloring Material B — 100 100 — — — — — (OH Value = 9.8) ColoringMaterial C — — — — — — — — (OH Value = 15.7) Coloring Material D — — —100 — — — — (OH Value = 3.8) Coloring Material E — — — — 100 100 — — (OHValue = 20.6) PTMG-1000M 5 2 2 3 5 5 5 5 OH Value of Resin (mg KOH/g)30.0 31.2 31.2 17.0 39.2 41.4 30.0 30.0 Crosslinking Coronate UK 22.220.8 25.4 6.8 19.4 29.8 25.9 25.9 Agent (B-4) (part) Eq. Wt. ofCrosslinking Agent 1.2 1.1 1.3 0.8 0.8 1.1 1.4 1.4 based on OH GroupThickness (μm) 50 40 40 50 50 50 50 50 Destructible Acrylic Compo-2100U7 50 20 50 50 50 50 50 20 Layer Resin sition Coloring Material A100 — — 100 100 100 — — (OH Value = 5.3) Coloring Material C — 50 50 — —— — 100 (OH Value = 15.7) Coloring Material D — — — — — — — — (OH Value= 3.8) Coloring Material E — — — — — — 100 — (OH Value = 20.6)PTMG-1000M 5 5 2 5 5 5 5 3 OH Value of Resin (mg KOH/g) 25.2 24.9 34.025.2 25.2 25.2 33.0 21.0 Art Pearl GR-300 16 16 16 16 16 16 16 16Crosslinking Coronate HK 22.2 14.0 23.7 19.3 28.6 22.5 24.2 18.1 Agent(C-4) (part by weight) Eq. Wt. of Crosslinking Agent 1.2 1.3 1.3 0.8 1.41.1 0.8 1.4 based on OH Group Thickness (μm) 55 60 60 55 100 100 55 55Adhesive Compo- PE-121 100 100 100 100 100 100 100 100 Layer sitionCK-401 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 Thickness (Mm) 30 30 30 30 30 3030 30

TABLE 7 User Marking Test Attachment Label Heat Resistance to Laser HeatNon-reusability Workability Resistance Strike-Through SharpnessLegibility Resistance Example 14 B good good good good good good Example15 A good good good good good good Example 16 A good good good pood goodgood Example 17 A good good good good good good Example 18 A good goodgood good good good Example 19 A good good good good good good Example20 A good good good good good Rood Example 21 B good good good good goodgood Example 22 B good good good good good good Example 23 A medium goodgood good good good Example 24 A good good good good good good Example25 A good good good good good good Comparative Example 11 E good goodgood good good good Comparative Example 12 D poor good good good goodgood Comparative Example 13 D medium good good good good goodComparative Example 14 E medium good good good good good ComparativeExample 15 E poor good good good good good

The physical properties of the laser markable brittle laminates obtainedin Examples 14 to 25 and Comparative Examples 11 to 15 were measured orevaluated in accordance with the methods (4) to (8) described supra andthe methods (9) and (10) described infra.

(9) Hydroxyl Value

A sample to be analyzed weighing 2.00 g was put in a flat bottom flask,and 5 ml of an acetylation reagent (prepared by putting 25 g of aceticanhydride in a 100 ml measuring flask and adding pyridine to make 100ml) was added thereto, followed by heating at 95° to 100° C. for 1 hour.One milliliter of water was added thereto, and the heating was continuedfor an additional 10 minutes, followed by cooling to room temperature.To the system were added 5 ml of ethanol and a few drops of aphenolphthalein solution. A 0.5 mol/L ethanolic potassium hydroxidesolution was added until the titration end point (when the deep pinkcolor of the system did not disappear any more). Separately, a blanktest was carried out. The hydroxyl value of the sample was calculatedfrom formula:A=(B−C)×f×28.05/Swhere A is a hydroxyl value: B is the amount (ml) of a 0.5 ml/Lethanolic potassium hydroxide solution used in the blank test; C: is theamount (ml) of a 0.5 ml/L ethanolic potassium hydroxide solution used inthe titration; f is a factor of the 0.5 ml/L ethanolic potassiumhydroxide solution; and S is the mass (g) of the sample.(10) Non-Reusability

A 1.5 cm wide, 5 cm long piece of the laminate was attached to a whitecoated plate and allowed to stand at 23° C. for 72 hours and thenremoved from the coated plate using a cutter knife. The removed laminatewas checked if it was reusable or non-reusable as a result of, forexample, destruction. The test was repeated ten times per sample. Thenon-reusability of the laminate was rated on an A to E scale as follows.

A: The sample became non-reusable nine or more times out of ten.

B: The sample became non-reusable eight times out of ten.

C: The sample became non-reusable seven times out of ten.

D: The sample became non-reusable six times out of ten.

E: The sample became non-reusable five or fewer times out of ten.

INDUSTRIAL APPLICABILITY

The laser-markable laminates according to the first and second aspectsof the invention do not suffer from appearance defects, such as a crack,nor fall off even when exposed to severe temperature conditions and areattachable even to a curved surface with conformability. For use as alabel, they have good workability in being attached to a substrate and,upon being peeled off the substrate, are damaged to become non-reusable.

The laminate according to the third aspect of the invention withstandsuse under high temperatures of 150° C. or higher and is laser-markablesuch that the pigmented layer thereof is ablated on imagewiseirradiation with laser light to expose the irradiated part of the baselayer whereby to achieve desired marking.

The invention claimed is:
 1. A laser-markable, acrylic resin-basedlaminate comprising: a pigmented layer being made of a crosslinkedacrylic resin obtained by crosslinking an acrylic resin composition witha melamine crosslinking agent and being adapted to provide the outermostsurface of the laminate when attached to a substrate, the acrylic resincomposition having a hydroxyl value of 10 to 100 mg KOH/g and comprisingan acrylic polymer having a reactive functional group, cellulose acetatebutyrate, and a pigment, a base layer laminated with the pigmented layerbeing made of a crosslinked acrylic resin obtained by crosslinking anacrylic resin composition with an isocyanate crosslinking agent andproviding a visibly distinguishable color difference from the pigmentedlayer, the acrylic resin composition having a hydroxyl value of 18 to 40mg KOH/g and comprising an acrylic polymer having a reactive functionalgroup, a glycol compound, and a coloring material containing an acrylicresin having a reactive hydroxyl group and a pigment dispersed in theacrylic resin, and a destructible layer laminated with the base layer,being made of a crosslinked acrylic resin obtained by crosslinking amixture of an acrylic resin composition and polymer beads with anisocyanate crosslinking agent, the acrylic resin composition having ahydroxyl value of 20 to 35 mg KOH/g and comprising an acrylic polymerhaving a reactive functional group, a glycol compound, and a coloringmaterial containing an acrylic resin having a reactive hydroxyl groupand a pigment dispersed in the acrylic resin, wherein the laminate has athickness of 100 to 200 μm.
 2. The laser-markable, acrylic resin-basedlaminate according to claim 1, wherein the amount of the isocyanatecrosslinking agent of each of the base layer and the destructible layeris 1.1 to 1.3 equivalent weights based on the hydroxyl value of theacrylic resin composition of the respective layers.
 3. A laser-markablelabel comprising the laser-markable, acrylic resin-based laminateaccording to claim 1 and an adhesive layer on the side of the laminateopposite to the pigmented layer.
 4. The laser-markable label accordingto claim 3, being adapted to be imagewise irradiated with laser light toablate the pigmented layer to form an image and attached to a substrate,the imaged pigmented layer being adapted to be destroyed to make thelabel non-reusable when the label is peeled off the substrate.
 5. Alaser-markable label comprising the laser-markable, acrylic resin-basedlaminate according to claim 2 and an adhesive layer on the side of thelaminate opposite to the pigmented layer.